British workers at GlaxoSmithKline are bracing themselves for bad news this week as the pharmaceuticals group prepares to announce plans to shed about 10% of its global workforce.

The company, which employs 100,000 people across the world, is seeking to slash costs in the face of the threat to profits from cheap, generic "copycat" versions of some of its biggest selling drugs as they lose their patent protection.

Glaxo employs about 18,000 people in Britain. The company runs manufacturing operations across the UK, including sites at Ware, Maidenhead and Worthing.

News of the job losses are expected to be revealed when Glaxo reports its results on Thursday. Union leaders are becoming increasingly concerned that British workers are being sacrificed by multinational companies ahead of European workers because UK employment laws are more lax than those on the continent. The job losses are particularly galling for the government as it has pinned its hopes for economic growth on exactly the sort of high-specification manufacturing and development that is carried out by the drugs industry.

The job losses are part of a cost-cutting drive by GSK's new chief executive, Andrew Witty. Some analysts say the cuts could be deeper than the 10,000 mooted over the weekend.

Analysts say that with growing competition, drug companies must make cuts or seek mergers. Last week, US firm Pfizer announced a $68bn (£47bn) bid for Wyeth, a smaller rival.

Witty has indicated that, for the moment, he does not intend to pursue major acquisitions, preferring instead to expand in emerging markets.